Ever since man has utilized ships upon the sea, one of the outstanding problems has been biological fouling of the underwater surfaces. Numerous methods and substances for coating the underwater portions of ship's hulls against such fouling have been utilized with variable success. Marine organisms, such as slimes and barnacles, despite modern coatings technology, have found ways to become attached to coatings in an unacceptable manner. Present technology can generally be classified into one of two methods: methods that prevent the attachment of the organisms by toxic leaching coatings, which over time slowly leach a material toxic to adhering marine organisms; and fouling release coatings, which to some degree are anti-adhesive to marine organisms, being manufactured from polymers which the organisms find it relatively more difficult to adhere to, such as fluorinated or silicone polymers, or coatings containing polytetrafluoroethylene powder as pigment. The latter coatings and methods have been extensively investigated by Griffith, Bultman, O'Rear, Field, and coworkers at the Naval Research Laboratories and reported in the literature and in a number of U.S. Pat. Nos., e.g. NRL report 7127 (Aug. 1970); Polym. Prep., Am. Chem. Soc., Div. Polym. Chem. 14 (2), 1148-53 (1973); Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 1 p. 8-9, 1978; Polymer, May 1985 p. 27; Naval Engineers J., p. 129-132, April 1980., Ind. Eng. Chem. Prod. Res. Dev. 1986, 25, 572-7; U.S. Pat. Nos. 4,157,358, 4,045,408, 3,720,639, 4,132,681, 4,284,747, 3,872,045, 4,633,023, 3,852,222, 4,452,998, 3,549,591, and 3,879,430.
The toxic leaching method maintains a fairly clean underwater surface effectively for approximately one year, after which time the coating containing the toxicant must be removed and replaced, having been overgrown by marine organisms and depleted of its toxicant. Even if few organisms had been growing on its surface, the toxicant therein would still have been leaching out into the sea, thus adding over the long term to the pollution thereof.
The anti-adhesive or fouling release coating provides a surface inherently difficult for an organism to bond to by virtue of its chemical composition or physical surface characteristics or a combination of both. The fluorinated epoxy polymer and silicone surfaces described by Griffith, and others, such as exemplified by U.S. Pat. Nos. 4,157,358, 4,045,408, 3,720,639, 4,132,681, 4,284,747, 3,872,045, 3,852,222, 3,549,591, and 3,879,430, are of this type and yield surfaces which are not immune to biological growth, but growth which can be removed from the surfaces by the force of water sprays or by high pressure water washes in combination with hand or machine wiping or brushing.